Device for testing electric currents.



No. 755,382. PATENTED MAR. 22, 1904.

' 0. OLIVER. I

DEVICE FOR TESTING ELEGTRIC GURRENTS.

' APPLICATION FILED NOV. 29, 1902.

no MODEL.

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Z M I] c 0? F295. 1 5 W F2 6 a/ fiy CZ 0% 5-4 5 c c1 7 UNITED STATESPatented March 22, 1904:.

PATENT OEEIcE.

DEVICE FOR TESTING ELECTRIC CURRENTS.

SPECIFICATION forming part of Letters Patent No. 755,382, dated March22, 1904.

Application filed November 29, 1902. $.erial1I0. 133,200. (No model.)

To all whom it may concern:

Be it known that I, CHARLES OLIVER, electrical engineer, a subject ofthe King of Great Britain, residing at Woolwich, in the county of Kent,England, have invented a Device for TestingElectric Ourrents,of whichthe following is a specification.

This invention relates to a new or improved detector or appliance foruse in testing for electric currents.

Heretofore in order to ascertain if an electric wire or electric circuit(or any part of any machine or metal-work) is alive sometimes agalvanometer (or other means, such as incandescent electric lamp) hasbeen employed, While in many cases the operative or person desiring tomake such test simply momentarily touches the Wire or part in question,so as to receive a shock or indication to thereby ascertain in thiscrude Way whether the wire or circuit or part is alive or not. Suchmethods of testing as heretofore employed have various drawbacks,and,moreover,the last-named crude method is usually exceedinglydisagreeable or dangerous to the operator and for high voltagesimpossible owing to the danger involved.

Now my present invention is designed to overcome the aforesaid drawbacksand comprises a detector or appliance for the abovenamed purpose whichis very simple and inexpensive to produce, is very compact, andportable, (same being adapted to be carried in the pocket of the user,)and whereby the person using same can without danger or discomfortreadily ascertain if any wire or circuit or part to be tested is aliveor not, even at dangerous voltages.

According to my invention I take any suitable insulating or non-"conducting material (advantageously of a non-breakable or not easilybreakable character) and I so treat such material as to make same of orproduce in or on same a suitable low electrical conductivity, and thismaterial of low electrical conductivity or having low electricalconductivity I arrange and mount in any suitable cap, case, or coveringor other means for holding or applying or holding and applying same inuse, as hereinafter described.

My invention may be carried into practice as follows: I take aninsulating material, such as cedar wood or other suitable wood or othersuitable material through which little or no shock can be felt when putin circuit, and I dip or otherwise coat or apply to same a solution ofshellac and black-lead in spirit, and when the coating is dry I polishor rub the surface, and thereby produce a low electrical conductivity inor upon said material; but I do not confine myself to shellac andblack-lead, as aforesaid, as it will be obvious that other materials ofsuitable conductivity might be employed to produce the desired lowelectrical conductivity for my purpose. For instance, another method ofcarrying out my present invention would be to mix black-lead Withporcelain and form same into sticks or pencils or other-shaped devicesof any suitable form and then bake or fire same.

In carrying my present invention into practice I take a piece of anysuitable size and shape of the aforesaid material of low electricalconductivity, (which for the sake of brevityI shall hereinafter refer toas the resisting material,) say, for instance, a piece of about the sizeof an ordinary pocket-pencil, (say a strip of such material about twoinches long and of flattened form,) as illustrated by way of example inthe accompanying drawings, in which- Figure 1 is a view of the flat sideof said resisting material, showing same with a metal cap fittedthereto, as and for the purposes hereinafter explained. Fig. 2 is a sideview of asheet-metal case of flattened form adapted to receive andinclose therein said strip of resisting material. Fig. 3 shows thesheet-metal case inclosing the resisting material. Fig. 4: is an edgeview of Fig. 3, showing the springmouth to said sheet-metal case. Fig. 5is a longitudinal sectional view on line 5 5, Fig. 4. Fig. 6 shows amodification, as hereinafter explained.

The strip or rod of resisting material a has one end or part providedwith a metal cap 6, or instead of employing such metal cap I) such endor part of said resisting material maybe treated in any suitable mannerso as to render such end or part more highly conductive than the otherpart, and such end or part, as well as such metal cap 6, I shall for thesake of brevity hereinafter refer to as the metal cap.

0 is sheet-metal case of flattened form, adapted to receive therein saidstrip of resisting material a, and also, if desired, the metal cap 6 orpart thereof may be adapted to slide into or onto said cover 0, or inorder to prevent the possibility of the appliance being wrongly used(2'. (5., while the metal cap 6 is incontact with the cover 0) and thecurrent passing direct from the metal cap 6 to the metal case cI maymake the resisting material a longer than the case 0, as shown in Fig.6, or of such length or shape as to render it impossible for the metalcap 6 to touch the metal cover 0 when the latter is slid over theresisting material a.

In order to clip or hold the resisting material a in any desiredposition, (d. 0., when drawn out of or inserted in the cover 0 to agreater or less eXtent,) the end 0 may be formed s pring-mouthed,forinstance, by forming said cover 0 with longitudinal slits 0 as shown inFig. 4:, whereby the spring ends 0 0 will tend to grip and hold firmlybetween same the cap 6 or the resisting material in whatever positionsame may be placed thereinbetween, while at same time making ormaintaining electric contact therewith.

The operation is as follows: By drawing out the resisting material a toa greater or less extent from the aforesaid case 0 and then holding theease or cover 0 of the detector or appliance in one hand and touchingone wire or terminal or part in question with the cap 6 on saidappliance and touching with the other hand (or otherwise makingconnection through the body to) the other pole of the circuit thereby agentle shock or indication will be received if the wire or part be aliveand the current be at sufficient voltage, and by sliding the resistingmaterial a in or out of the case 0, and so varying the length ofresistance between the metal cap 6 and the case 0, thereby the strengthof shock or indication will be diminished or increased. Or theinstrument may be used as follows: The resisting material a, with themetal cap 6 thereon, may be completely withdrawn from the case 0 andgrasped between the fingers at any desired point along the length ofsaid resisting material a, and then by touching one wire or terminal orpart with the metal cap 6 and making connection with the other pole, asbefore, a gentle shock or indication will be obtained as before. Or theinstrument may be used as follows: The material a, with cap 6 thereon,may be completely withdrawn from the case 0 and reversed and the outerend of the cap 6 inserted in the spring-mouth of the case 0, and thenthe material a is grasped between the fingers, as last described, andthe wire or terminal or part to be tested is touched with the case a.

In Fig, 6 I have illustrated an arrangement in which theresistingmaterial a is rather longer than the case 0, so as to therebyrender it impossible for the cap 6 to touch the case 0 under anycircumstances when the latter is in position on the resisting material.

It will be obvious that I do not confine myself to the formillustratedor to any particular form of case or holder or means forcarrying this detector or appliance for use as aforesaid, nor do Irestrict myself to the employment of any such case or holder at allshould it be desired to dispense therewith.

If desired, my invention may be carried out in the form of alead-pencil-tliat is to say, the resisting material of low electricalconductivity may be provided with a lead core, as in an ordinarylead-pencil, and same may be used either with or without a case. Also,if desired, my invention may be carried out vice versa-that is, I mayemploy the insulating or non-conducting material on the exterior or toform the exterior surface, the conducting material being located insidesuch nonconducting material.

Having now described my invention, what I claim as new, and desire tosecure by Letters Patent of the United States, is-

1. A detector or appliance for use in testing for electric currents,comprising a rod of insulatory material provided with a coating of asubstance of low electrical conductivity, and means at one end of saidrod rendering the end more highly conductive than the remainder of therod, substantially as set forth.

2. A detector or appliance for use in testing for electric currents,comprising a rod of resisting material of low electrical conductivity,means at one end of said rod rendering the end more highly conductivethan the rod itself, and a case or cover for said rod, substantially asset forth.

3. A detector or appliance for use in testing for electric currents,comprising a rod of insulatory material provided with a coating of asubstance of low electrical conductivity, and a metal cap at one end ofsaid rod, substantially as set forth.

4. A detector or appliance for use in testing for electric currents,comprising a rod of resisting material of low electrical conductivity, ametal cap at one end of said rod, and a case or cover for said rod,substantially as set forth.

5. A detector or appliance for use in testing for electric currents,comprising a strip or rod of wood provided with a coating of a sulstance of low electrical conductivity, substantially as set forth.

6. A detector or appliance for use in testing for electric currents,comprising a strip or rod of wood provided with a substance of lowelectrical conductivity, and a metal cap at one end of said strip orrod, substantially as set forth.

7 A detector or appliance for use in testing for electric currents,comprising a strip 01' rod of Wood provided with a coating of asubstance of low electrical conductivity, a metal cap at one end of saidstrip or rod, and a case or cover for said strip or rod, substantiallyas set forth.

8. A detector or appliance, for use in testing for electric currents,comprising a strip or rod of Wood, a coating of black-lead and shellacthereon, and a metal cap at one end thereof, substantially as and forthe purposes hereinbefore set forth.

9. A detector or appliance, for use in testing for electric currents,comprising a strip or rod of Wood, a coating of black-lead and shellacthereon, a metal cap at one end thereof and a case or cover toreceivetherein said resisting material, substantially as and for thepurposes hereinbefore set forth.

In Witness whereof I have hereunto set my hand in presence of tWoWitnesses.

CHARLES OLIVER. Witnesses:

H. D. JAMEsoN, A. NUTTING.

